An association between Anorexia Nervosa and affective disorders has been suggested. Affective disorders are associated with catecholamine abnormalities. Platelet MAO activity has been reported to be reduced in depressive disorders; plasma cyclic AMP has been studied as a possible reflector of peripheral CA receptor activity and decreased levels of MHPG have been found in urine of depressed patients. In addition, an association has been reported between certain HLA antigens and ABO blood types and affective disorders. We hypothesize that Anorexia Nervosa is associated with affective disorders, possibly via a common underlying pathophysiology. Thus similar biochemical abnormalities would be found in two disorders. We, therefore, propose to study platelet MAO activity, urine MHPG, plasma cyclic AMP, HLA antigens and ABO blood types in Anorexia Nervosa patients and normal controls. Moreover, tricyclic antidepressant drugs are effective in the treatment of depression, and they also effect CA metabolism. Recent case reports and single-blind trials using amitriptyline in the treatment of Anorexia Nervosa describe good results. We further hypothesize that Anorexia Nervosa would respond favorably to amitriptyline therapy, therefore, we propose to study the effect of amitriptyline in 40 Anorexia Nervosa patients in a double-blind, placebo-controlled design. Clinical state and drug response will be measured weekly. Amitriptyline blood levels will be assayed for correlation with clinical response.